The present invention relates to a storage system that controls data-in data storage devices such as hard disk drives (hereinafter called ‘HDDs’), and also to a method for controlling the storage system. This invention particularly relates to power supply control for the data storage devices.
With the increase in the amount of data dealt with in computer systems each having a storage system and host system(s), such as server(s) or host computer(s) connected to the storage system via a communication path such as a network, the capacity of the storage areas in the storage systems has also expanded. In these storage systems, logical volumes accessible by the host systems are defined so that the host systems access physical storage areas allocated to the logical volumes, thereby enabling the input/output of data to/from the data storage devices.
Recently, because the amount of data dealt with in host systems has increased dramatically, the size of volumes, i.e., the storage capacity of the volumes, also has had to be increased to a large extent. If the host systems are each provided with large-size storage areas from the beginning, they will not have a shortage of storage capacity and it will be unnecessary to expand the size of the storage areas at a later point in time. However, if the host systems—computers—do not use a large amount of data, some of the storage areas allocated to the host systems remain unused and because the storage areas are fixed to the host systems, these unused storage areas are wasted.
In light of this, Japanese Patent Laid-Open (Kokai) Publication No. 2003-15915 proposes, for the purpose of expanding the storage capacity of logical volumes by dynamically allocating storage areas having appropriate capacities from among collectively-managed storage areas to the logical volumes during operation of host systems, a storage system that monitors logical block addresses for read or write I/O from the host systems to logical volumes in data storage devices; dynamically expands the storage areas of the logical volumes based on the logical block addresses; and also expands the storage area of a logical volume when an instruction unit in the host systems commands a volume server to expand the capacity of the logical volume.
Incidentally, Japanese Patent Laid-Open (Kokai) Publication No. 2005-4349—prior art related to this invention—aims to provide a mechanism where, when a storage apparatus (storage system). lacks storage areas, storage resources of another storage apparatus are effectively used without adding physical disks to the lacking storage areas, and discloses a computer system. where a first storage apparatus judges whether it can write data in a first storage area when it receives a data write request from an information processor; and when the judgment is negative, the first storage apparatus requests information for judging whether it can secure a second storage area for storing the data from a second storage apparatus; and where, in response to this request, the second storage apparatus sends the information regarding whether the second storage area can be secured for the first storage apparatus to the first storage apparatus; the first storage apparatus judges whether it can secure the second storage area based on the information; and if the judgment is positive, the first storage apparatus sends the data to the second storage apparatus so that it will be stored in the second storage area.